1. Field of the Invention
This invention relates to a system for restraining the body of an occupant in a vehicle to reduce the extent and severity of injuries during a crash. More specifically, the invention relates to a seat belt restraint system which incorporates an inflatable tubular section in the torso section of the belt. The inflatable tubular section can be made of a woven or braided tube of continuous high-strength fibers or can alternatively be made from an extruded net or from a woven net. The restraint system reduces the extent and severity of both primary and secondary injuries to vehicle occupants.
2. Background of the Invention
Conventional seat belts are designed to protect the occupants of vehicles such as automobiles, trucks, vans, airplanes and helicopters from primary injuries during an accident. Primary injuries are injuries caused by the initial impact of the occupants against the interior of the vehicle. However, the protection provided by conventional seat belts against primary injuries may sometimes be inadequate. For example, slack in the seat belts may lead to unnecessarily serious primary injuries. In side impacts conventional belts do not provide occupant head protection on the struck side of the vehicle. Moreover, the seat belts themselves may often be responsible for secondary injuries, since the load from the seat belts is distributed only over small areas of the occupant's body. However, some prior art belts have tried to lessen primary injuries by incorporating an inflating mechanism into the seat belt restraint.
For example, U.S. Pat. No. 5,282,648, which is incorporated by reference herein, discloses an inflatable body and head restraint system, wherein inflatable bladders are attached to the shoulder straps of a harness restraint. The bladders are stowed partially underneath and partially on top of harness straps. This configuration provides stability and prevents the bladders from rolling out of position during inflation. During a crash, the bladders inflate to protect the upper body, primarily the head and neck of the occupant.
Additionally, U.S. Pat. Nos. 3,948,541 and 3,905,615 to Schulman disclose another inflatable body and head restraint system, wherein a bladder is securely affixed to shoulder straps and a lap belt. The bladder has chin, chest, and pelvic bags. Upon impact, the bladder automatically inflates to cushion the pelvic areas and to prevent forward rotation of the head. However, upon inflation the bladder tends to roll out from its position under the shoulder straps. Also, because the bladders are constricted by the harness, portions of the bladder are subjected to high pressures, which can lead to splitting of the bladder.
Simple inflatable body restraints are also disclosed in U.S. Pat. Nos. 3,682,498 and 4,348,037 to W. Rutzki and B. Law et al, respectively. These patents disclose inflatable protective devices that are located in or under the seat harnesses to which they are attached. These inflatable body restraints are subject to roll-out and seam or web splitting problems.
In yet another prior art seat belt disclosed in, U.S. Pat. Nos. 3,841,654 and 3,970,329 both to Lewis, a vehicle seat system which comprises a seat belt having an inflatable section is shown. When a collision is detected, the inflatable section is inflated to protect the person wearing the seat belt.
The prior art inflatable seat belt structures, such as those identified above, generally use a unitary inflatable section made from a tightly woven material, such as 420 denier nylon, which is conventional air bag material. When deployed, the inflatable section will contract in length somewhat because the inflation pressure causes it to go from a flat, generally 2-dimensional shape to a 3-dimensional cylindrical shape. However, only the ends of the inflatable section contract as they fill and assume a hemispherical shape. This causes only the ends of the inflatable section to shorten, thus shortening the overall length of the inflatable section. The fibers of the material do not change their orientation: the two sets of fibers in the material remain roughly perpendicular to each other throughout the inflation process.
In the case of the typical inflatable seat belt made of conventional air bag material as described above, the maximum theoretical amount that the inflatable structure contracts upon inflation, in an unconstrained condition prior to being loaded by the occupant, is based only on the width of the flat material. If inflation results in a relatively small cylindrical diameter then a relatively small contraction, or shortening, of the length of the seat belt will occur. The calculation for determining the amount of contraction that will occur with conventional air bag material upon inflation and in an unconstrained condition is as follows: EQU Lf-Li=X (1)
where:
X is the amount of contraction PA1 Lf is the length of flat, uninflated, material PA1 Li is the length of unconstrained inflated material, PA1 Df is the width (flat diameter) of flat, uninflated, material PA1 Di is the diameter of unconstrained inflated material.
and EQU Li=Lf-(Df-Di) (2) EQU Di=2/.pi. (Df) (3) EQU Lf-Li=Df(1-2/.pi.) (4)
where:
As seen in equation (4), the length reduction depends solely on the uninflated width (flat diameter) of the material.
For example, an inflatable structure having a flat diameter of 20 cm and a flat length of 100 cm has a maximum achievable contraction of 7.3 cm or roughly 7% in the absence of any load. In an actual application, with the belt under tension, the contraction would be much less, e.g., about 3%. This degree of contraction would provide restraint that is only slightly greater, and, thus, only slightly more protective than a conventional seat belt.
The construction disclosed in U.S. Pat. No. 3,888,503 to Hamilton comprises an inflatable restraining band having a series of sections, some of which are inflatable to a greater degree than others interconnecting them. In the Hamilton design, contraction occurs upon inflation only at each end of each section, and because the sections are of variable inflatable size, the amount of contraction varies along the structure. By not allowing full expansion of interconnecting portions or sections of the inflatable band more hemispherical "ends" occur thus the overall band is foreshortened to a greater extent than otherwise on expansion, which causes greater tensioning of the band against the occupant restrained.
Hamilton provides greater protection than the conventional inflatable seat belt in terms of the provision of greater restraint and hence improves upon a conventional inflatable seat belt. However, the restraint that results from Hamilton's patent is still significantly less than the restraint provided by the present invention.
None of the patents described above provide the important advantage of the significant contraction which occurs in the present invention as the inflatable structure expands upon inflation.